In a printer using a pen, the pen opposed to a platen is pushed by a push member such as hammer in printing so that the tip of pen is brought into contact with a printing paper on the front face of platen.
And the push member is driven by the rotation of a drive shaft, for example, as shown in commonly owned U.S. Pat. No. 4,405,931, issued to Fugisawa on Sept. 20, 1983. A mechanism is proposed which comprises a lever provided on one end of the drive shaft and a solenoid for pivoting the lever and thus the drive shaft with its attraction.
By this method, however, is consumed a great amount of electric power since current is left supplied so long as the solenoid attracts the lever.
Also, a spring for exerting a force opposite to the direction of attraction is needed to return the solenoid from the attraction state so that electric power necessary for the attraction of solenoid is further increased.
When a self-holding type solenoid is used, current does not need to be supplied while the solenoid attracts. However, current needs to be supplied not only in the attraction, but also at the release from attraction in the reverse direction so that a drive circuit is complicated. Also, in the release of attraction, the self-holding force needs to be overcome so that the maximum current is increased.
Also in the case of solenoid, an operational distance in which the effective attraction is generated is short so that the operational distance should be expanded by any methods.
A pen changing mechanism operated by a change lever is shown in commonly owned Japanese Patent Publication No. 59-26267, and thus is considered to be conventional and will not be described further herein.